However, most algorithms are only applicable to single-modal image registration. With the increasing requirements of multi-source image registration, several algorithms for multi-modal image registration were proposed.
Based on SIFT algorithm, Chen et al [1]} proposed a partial intensity invariant feature descriptor (PIIFD) for multi-source retinal image registration, which has intensity and rotation invariance but is unable to deal with scale differences.
PSO-SIFT [2]} introduces a new gradient definition and an enhanced feature matching method for the registration of remote sensing images with intensity differences.
Radiation-variation insensitive feature transform (RIFT) [3]} proposes a maximum index map (MIM) for feature description, which has high intensity invariance, but low rotation invariance, and is not scale invariant.
Most of the research on multimodal image registration is focused on medical images. However, except for some differences in image characteristics and details, the multi-source remote sensing image registration has little difference in essence with medical image registration, so the algorithms also have universality.
